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Date: Wed, 23 Sep 2015 21:49:36 +0200
From: Peter Nørlund <pch@...bogen.com>
To: netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
James Morris <jmorris@...ei.org>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Patrick McHardy <kaber@...sh.net>,
Peter Nørlund <pch@...bogen.com>
Subject: [PATCH v4 net-next 1/2] ipv4: L3 hash-based multipath
Replaces the per-packet multipath with a hash-based multipath using
source and destination address.
Signed-off-by: Peter Nørlund <pch@...bogen.com>
---
include/net/ip_fib.h | 14 ++++-
net/ipv4/fib_semantics.c | 140 +++++++++++++++++++++++++---------------------
net/ipv4/route.c | 16 ++++--
3 files changed, 98 insertions(+), 72 deletions(-)
diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index a37d043..c454203 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -79,7 +79,7 @@ struct fib_nh {
unsigned char nh_scope;
#ifdef CONFIG_IP_ROUTE_MULTIPATH
int nh_weight;
- int nh_power;
+ atomic_t nh_upper_bound;
#endif
#ifdef CONFIG_IP_ROUTE_CLASSID
__u32 nh_tclassid;
@@ -118,7 +118,7 @@ struct fib_info {
#define fib_advmss fib_metrics[RTAX_ADVMSS-1]
int fib_nhs;
#ifdef CONFIG_IP_ROUTE_MULTIPATH
- int fib_power;
+ int fib_weight;
#endif
struct rcu_head rcu;
struct fib_nh fib_nh[0];
@@ -312,7 +312,15 @@ int ip_fib_check_default(__be32 gw, struct net_device *dev);
int fib_sync_down_dev(struct net_device *dev, unsigned long event);
int fib_sync_down_addr(struct net *net, __be32 local);
int fib_sync_up(struct net_device *dev, unsigned int nh_flags);
-void fib_select_multipath(struct fib_result *res);
+
+extern u32 fib_multipath_secret __read_mostly;
+
+static inline int fib_multipath_hash(__be32 saddr, __be32 daddr)
+{
+ return jhash_2words(saddr, daddr, fib_multipath_secret) >> 1;
+}
+
+void fib_select_multipath(struct fib_result *res, int hash);
/* Exported by fib_trie.c */
void fib_trie_init(void);
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 064bd3c..0c49d2f 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -57,8 +57,7 @@ static unsigned int fib_info_cnt;
static struct hlist_head fib_info_devhash[DEVINDEX_HASHSIZE];
#ifdef CONFIG_IP_ROUTE_MULTIPATH
-
-static DEFINE_SPINLOCK(fib_multipath_lock);
+u32 fib_multipath_secret __read_mostly;
#define for_nexthops(fi) { \
int nhsel; const struct fib_nh *nh; \
@@ -532,7 +531,67 @@ errout:
return ret;
}
-#endif
+static void fib_rebalance(struct fib_info *fi)
+{
+ int total;
+ int w;
+ struct in_device *in_dev;
+
+ if (fi->fib_nhs < 2)
+ return;
+
+ total = 0;
+ for_nexthops(fi) {
+ if (nh->nh_flags & RTNH_F_DEAD)
+ continue;
+
+ in_dev = __in_dev_get_rcu(nh->nh_dev);
+
+ if (in_dev &&
+ IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev) &&
+ nh->nh_flags & RTNH_F_LINKDOWN)
+ continue;
+
+ total += nh->nh_weight;
+ } endfor_nexthops(fi);
+
+ w = 0;
+ change_nexthops(fi) {
+ int upper_bound;
+
+ in_dev = __in_dev_get_rcu(nexthop_nh->nh_dev);
+
+ if (nexthop_nh->nh_flags & RTNH_F_DEAD) {
+ upper_bound = -1;
+ } else if (in_dev &&
+ IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev) &&
+ nexthop_nh->nh_flags & RTNH_F_LINKDOWN) {
+ upper_bound = -1;
+ } else {
+ w += nexthop_nh->nh_weight;
+ upper_bound = DIV_ROUND_CLOSEST(2147483648LL * w,
+ total) - 1;
+ }
+
+ atomic_set(&nexthop_nh->nh_upper_bound, upper_bound);
+ } endfor_nexthops(fi);
+
+ net_get_random_once(&fib_multipath_secret,
+ sizeof(fib_multipath_secret));
+}
+
+static inline void fib_add_weight(struct fib_info *fi,
+ const struct fib_nh *nh)
+{
+ fi->fib_weight += nh->nh_weight;
+}
+
+#else /* CONFIG_IP_ROUTE_MULTIPATH */
+
+#define fib_rebalance(fi) do { } while (0)
+#define fib_add_weight(fi, nh) do { } while (0)
+
+#endif /* CONFIG_IP_ROUTE_MULTIPATH */
static int fib_encap_match(struct net *net, u16 encap_type,
struct nlattr *encap,
@@ -1094,8 +1153,11 @@ struct fib_info *fib_create_info(struct fib_config *cfg)
change_nexthops(fi) {
fib_info_update_nh_saddr(net, nexthop_nh);
+ fib_add_weight(fi, nexthop_nh);
} endfor_nexthops(fi)
+ fib_rebalance(fi);
+
link_it:
ofi = fib_find_info(fi);
if (ofi) {
@@ -1317,12 +1379,6 @@ int fib_sync_down_dev(struct net_device *dev, unsigned long event)
nexthop_nh->nh_flags |= RTNH_F_LINKDOWN;
break;
}
-#ifdef CONFIG_IP_ROUTE_MULTIPATH
- spin_lock_bh(&fib_multipath_lock);
- fi->fib_power -= nexthop_nh->nh_power;
- nexthop_nh->nh_power = 0;
- spin_unlock_bh(&fib_multipath_lock);
-#endif
dead++;
}
#ifdef CONFIG_IP_ROUTE_MULTIPATH
@@ -1345,6 +1401,8 @@ int fib_sync_down_dev(struct net_device *dev, unsigned long event)
}
ret++;
}
+
+ fib_rebalance(fi);
}
return ret;
@@ -1467,20 +1525,15 @@ int fib_sync_up(struct net_device *dev, unsigned int nh_flags)
!__in_dev_get_rtnl(dev))
continue;
alive++;
-#ifdef CONFIG_IP_ROUTE_MULTIPATH
- spin_lock_bh(&fib_multipath_lock);
- nexthop_nh->nh_power = 0;
- nexthop_nh->nh_flags &= ~nh_flags;
- spin_unlock_bh(&fib_multipath_lock);
-#else
nexthop_nh->nh_flags &= ~nh_flags;
-#endif
} endfor_nexthops(fi)
if (alive > 0) {
fi->fib_flags &= ~nh_flags;
ret++;
}
+
+ fib_rebalance(fi);
}
return ret;
@@ -1488,62 +1541,19 @@ int fib_sync_up(struct net_device *dev, unsigned int nh_flags)
#ifdef CONFIG_IP_ROUTE_MULTIPATH
-/*
- * The algorithm is suboptimal, but it provides really
- * fair weighted route distribution.
- */
-void fib_select_multipath(struct fib_result *res)
+void fib_select_multipath(struct fib_result *res, int hash)
{
struct fib_info *fi = res->fi;
- struct in_device *in_dev;
- int w;
-
- spin_lock_bh(&fib_multipath_lock);
- if (fi->fib_power <= 0) {
- int power = 0;
- change_nexthops(fi) {
- in_dev = __in_dev_get_rcu(nexthop_nh->nh_dev);
- if (nexthop_nh->nh_flags & RTNH_F_DEAD)
- continue;
- if (in_dev &&
- IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev) &&
- nexthop_nh->nh_flags & RTNH_F_LINKDOWN)
- continue;
- power += nexthop_nh->nh_weight;
- nexthop_nh->nh_power = nexthop_nh->nh_weight;
- } endfor_nexthops(fi);
- fi->fib_power = power;
- if (power <= 0) {
- spin_unlock_bh(&fib_multipath_lock);
- /* Race condition: route has just become dead. */
- res->nh_sel = 0;
- return;
- }
- }
-
- /* w should be random number [0..fi->fib_power-1],
- * it is pretty bad approximation.
- */
-
- w = jiffies % fi->fib_power;
+ for_nexthops(fi) {
+ if (hash > atomic_read(&nh->nh_upper_bound))
+ continue;
- change_nexthops(fi) {
- if (!(nexthop_nh->nh_flags & RTNH_F_DEAD) &&
- nexthop_nh->nh_power) {
- w -= nexthop_nh->nh_power;
- if (w <= 0) {
- nexthop_nh->nh_power--;
- fi->fib_power--;
- res->nh_sel = nhsel;
- spin_unlock_bh(&fib_multipath_lock);
- return;
- }
- }
+ res->nh_sel = nhsel;
+ return;
} endfor_nexthops(fi);
/* Race condition: route has just become dead. */
res->nh_sel = 0;
- spin_unlock_bh(&fib_multipath_lock);
}
#endif
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 80f7c5b..3dc83b6 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1659,8 +1659,12 @@ static int ip_mkroute_input(struct sk_buff *skb,
__be32 daddr, __be32 saddr, u32 tos)
{
#ifdef CONFIG_IP_ROUTE_MULTIPATH
- if (res->fi && res->fi->fib_nhs > 1)
- fib_select_multipath(res);
+ if (res->fi && res->fi->fib_nhs > 1) {
+ int h;
+
+ h = fib_multipath_hash(saddr, daddr);
+ fib_select_multipath(res, h);
+ }
#endif
/* create a routing cache entry */
@@ -2190,8 +2194,12 @@ struct rtable *__ip_route_output_key(struct net *net, struct flowi4 *fl4)
}
#ifdef CONFIG_IP_ROUTE_MULTIPATH
- if (res.fi->fib_nhs > 1 && fl4->flowi4_oif == 0)
- fib_select_multipath(&res);
+ if (res.fi->fib_nhs > 1 && fl4->flowi4_oif == 0) {
+ int h;
+
+ h = fib_multipath_hash(fl4->saddr, fl4->daddr);
+ fib_select_multipath(&res, h);
+ }
else
#endif
if (!res.prefixlen &&
--
1.7.10.4
--
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